1. Field of the Invention
The invention is in the field of telecommunications, and more specifically, it relates to a method of reselecting a cell by a mobile terminal in idle mode in a cellular telecommunication network in which the network sends to the mobile terminal a list containing information with regard to the cells to be identified, and in which the mobile terminal periodically performs a series of procedures of identifying the cells and a series of intersystem measurements on the identified cells.
The invention also relates to a GSM (Global System for Mobile communication)—UMTS (Universal Mobile Telephone service) dual mode mobile terminal comprising means for periodically performing a series of procedures of identifying UMTS cells and a series of intersystem measurements on the identified cells.
2. Description of the Related Art
In a cellular network, a mobile terminal is connected to a particular cell of the network, which will be referred to as current cell in the description below.
In order to prepare for reselection of a cell, the network sends to the mobile terminal the list of the neighboring cells in which the access technology is the same as the one implemented in the current cell, as well as the cells in which a different access technology is implemented.
When the measurements are performed on a radio access network whose technology is different from that in the serving cell, they are called “intersystem measurements.” The technical specifications of 3GPP (Third Generation Partnership Project) define a minimum duration, as well as a maximum duration for performing intersystem measurements on the identified cells, and a duration limit for performing reselection of a cell. However, these specifications do not impose the use of a particular algorithm of measurements to allow a GSM/UMTS dual mode terminal which is in an idle mode to reselect a UMTS cell from a current GSM cell. The idle mode is a mode in which the terminal is not in communication.
Recall that in idle mode, the terminal enters in a state “of sleep” in order to save the available energy in its battery to the maximum. However, the terminal must “wake up” from time to time to search for new cells and reselect one of them if the reception quality is better than the one measured in the current cell.